1. Technical Field
The present disclosure relates to a post-processing circuit for processing an image signal, and more particularly, to a post-processing circuit for processing an image signal according to frequency components of the image signal.
2. Discussion of Related Art
FIGS. 1A and 1B are block diagrams of a conventional post-processing circuit for eliminating noise from an image signal and sharpening an image corresponding to the image signal.
Referring to FIGS. 1A and 1B, the conventional post-processing circuits 10 and 20 sharpen an image signal after eliminating noise from the image signal. The conventional post-processing circuits 10 and 20, however, may not obtain an effective post-processing result because the noise elimination process and the sharpening process for improving the image quality have conflicting characteristics. That is, the conventional post-processing circuit 10 in FIG. 1A cannot recover high-frequency components of an image signal deleted through the noise elimination process even when the sharpening process is performed. On the other hand, the conventional post-processing circuit 20 in FIG. 1B has a limitation in eliminating noise effectively since the high-frequency components of the image signal are amplified during the sharpening process, which is performed before the noise elimination process is performed.
If an image signal is compressed based on a block-discrete cosine transform (block-DCT), a post-process, such as deblocking/deringing, is required to improve the image quality. That is, if the image signal is compressed based on the block-DCT, a non-continuous artifact may be generated at a block boundary. A ringing artifact is generated in an inside region of the block boundary due to the damaged high-frequency components of the image signal caused by the compression.
Therefore, a post-processing circuit for deblocking and deringing is required in order to post-process an image signal that has been compressed based on the block-DCT. Improved post-processing circuits for noise elimination and sharpening such as those shown in FIGS. 1A and 1B are also required.